In the known connecting devices for the simultaneous electrical connection of two neighbouring stator winding rods and the supply or removal of the cooling fluid to or from the hollow conductors of the stator winding rods, it is generally possible to differentiate between two design forms.
In the first type, (which is known for example from the Journal "BBC-Nachrichten" 60, Volume 1/1978, p. 6, FIG. 5), two rod ends, one above the other, are connected electrically by a strap. The hollow conductors of one rod protrude from the strap into one water chamber and are there brazed. Both water chambers are screwed onto an intermediate part fastened to the strap. Although, because of the distance between the water chamber and the rod end, it is possible to inspect satisfactorily the brazed connection between the hollow conductors and the water chamber, the distance has the disadvantage that the water chamber is not directly connected to the rod end. Even additional support for the water chamber by means of synthetic resin impregnated glass cords cannot completely prevent relative movements between the end of the rod and the water chamber. The hollow conductors are, of course, somewhat deformed by this relative movement. If the relative movement occurs during a vibration, the water chamber also vibrates relative to the end of the rod and the deformation procedure is repeated. The repeated deformation of the hollow conductor during this vibration relative to the end of the rod can lead to hollow conductor fractures.
In the second type of connection devices (such as is known, for example, from the German Offenlegungsschrift No. 2 803 015), the cooling fluid supply and the electrical connection between two neighbouring rod ends are combined in one component. Both rod ends are directly brazed to the water chamber. Although, in this case, there is no load on the hollow conductors, the danger of blockage of the hollow conductors by the material used for brazing does exist. Furthermore, the brazing process is expensive. Visual inspection of the braze and improvements to it are practically excluded. Furthermore, a special water chamber has to be designed and manufactured for each rod geometry.
A compromise (which is, however, expensive) between the two types described is provided by the connecting device according to Swiss Pat. No. 481 517. In this connecting device for the supply of the cooling fluid to the hollow conductors of the stator winding rods of electrical machines, the hollow and the solid conductors of the winding rod are collected by an attachment which is connected, on the one hand, to a supply connection for the cooling fluid and, on the other hand, electrically, to hollow and solid conductors. The hollow conductors protrude from the attachment into the internal space of the water chamber and are fastened so as to be liquid-tight in an insert bush. The insert bush is fastened to the end face of the attachment where the hollow conductors emerge. A packet of flexible strips, which provide the electrical connection between neighbouring rods, is also welded to the attachment. The free access to the ends of the hollow conductors makes it possible to ensure that the ducts in each hollow conductor are free and to check their hydraulic resistance. The free access to the ends of the hollow conductors also facilitates any repair work necessary. The attachment forms a rigid connection between the conductor rod ends and the water chamber. However, because of its triple function, it is very expensive. In addition, it increases the total overhang of the winding head to a substantial extent, it must be specially adapted for each rod geometry, and it requires substantial manipulation when bending the hollow conductors into place.